1. Field of the Invention
The present invention relates to an anticaking agent for an iron and steel slag, such as granulated blast furnace slag.
2. Background Art
A granulated blast furnace slag is formed by quenching and granulating a blast furnace slag, which is by-produced through a pig iron making process, with pressurized water sprayed thereon, followed by regulating in particle size by pulverization again depending on necessity, and is utilized as an alternate of natural sand as a material for civil engineering and a fine aggregate for concrete.
A granulated blast furnace slag is generally stored in the open air for a prolonged period of time before shipment or before use, and if the slag is stored as it is, the slag is consolidated and cannot be used as an alternate to natural sand. Accordingly, various anticaking agents have been proposed for preventing a granulated blast furnace slag from being consolidated during storage.
For example, JP-A-58-104050 discloses an anticaking agent containing as a major component a saccharide or a sugar alcohol, which is a reduced derivative of a saccharide, and JP-A-59-116156 discloses one containing sorbitol as a major component. JP-A-2001-58855 discloses one containing an alkylene oxide adduct of an aliphatic hydroxycarboxylic acid and/or a salt thereof, and JP-A-2002-179442 discloses one containing an aqueous solution of at least one of a carbonate, a hydrogen carbonate, ammonium carbonate and ammonium hydrogencarbonate. JP-A-54-96493 discloses an agent for producing a granulated blast furnace slag containing a polymer or a copolymer that contains as an essential constitutional component a water-soluble monoethylenic unsaturated monomer (such as sodium acrylate), and also discloses that the use of the agent provides anticaking effect on storage. JP-A-2003-160364 discloses a anticaking agent containing an acrylic acid based polymer. JP-A-2005-82426 discloses a anticaking agent containing a phosphonic acid derivative as an essential component, and further containing a polycarboxylic acid or a salt thereof and/or a sugar alcohol in suitable amounts.
However, the aforementioned anticaking agents having been developed provide a certain extent of anticaking effect but are still unsatisfactory, and in particular, they are insufficient in anticaking on long-term storage.
Among the anticaking agents, a phosphonic acid derivative or a salt thereof exhibits excellent anticaking effect, but the sole use thereof may bring about such problems as in cost, operation safety due to low pH thereof, corrosion of a storing container, a metallic piping and the like, and stability of a product thereof. The problems can be resolved by adding a polycarboxylic acid or a salt thereof and/or a sugar alcohol to a phosphonic acid derivative or a salt thereof to provide an anticaking agent with high performance, but there is still room for further improvement in anticaking with a small amount of an agent and maintenance of anticaking effect for a prolonged period of time.
A slag treated with an agent is often allowed to stand in the open air, and it is necessary to prevent the agent from being washed away from the surface of the slag by rain. Furthermore, there are increasing demands including reduction in cost on an anticaking agent, and further improvements thereof are expected.